Compressed air engine and flying object equipped therewith

ABSTRACT

A compressed air engine and a flying object using the engine are disclosed. The flying object includes the following elements. That is, the compressed air engine includes: a top member  11  provided with an air inlet  16 ; an upper cylinder  12 ; a lower cylinder  13 ; a bottom member  14 ; an air pipe, for passing of a compressed air; a shuttle  20  for performing up/down movements within a cylinder formed by the upper and lower cylinders; and a pair of pistons  21   a  and  21   b  over and under the shuttle respectively. The pair of the wings are symmetrically and pivotally assembled to the shuttle and the lower cylinder through securing shafts so as to perform up/down movements in accordance with the up/down movements of the shuttle. A compressed air container  2  is assembled to the bottom of the bottom member, for storing the compressed air.

FIELD OF THE INVENTION

The present invention relates to a compressed air engine and a flying object equipped with the air engine, in which a compressed air is injected into a compressed air container, and the compressed air is discharged to operate the engine by the force of the compressed air. More specifically, the present invention relates to a compressed air engine and a flying object equipped with the air engine, in which a compressed air is injected into a compressed air container, and the compressed air is discharged at a certain discharge rate, so that the discharging air would drive the compressed air engine. A pair of wings which are assembled to the compressed air engine are made flapped, and thus, lifting and propulsion forces are generated.

BACKGROUND OF THE INVENTION

Model planes are a kind of most popular sports articles for adults as well as for children. So far, many kinds of model planes have been manufactured for being used as toys, as sports articles and as recreation articles.

The model planes that have been manufactured so far can be classified into: those having no power-driving means; and those having a power-driving means. The model planes that are provided with the power-driving means include: propeller planes, jet planes, and helicopters with helical wings. They are usually controlled with a radio controller.

The present inventors have been making efforts to get rid of the conception of the conventional model planes to develop a flying object resorting to the flapping motions of wings like birds and insects.

The present inventor utilized the principle that insects and birds fly by the flapping motions of their wings. Thus, a compressed air was injected into a compressed air container to a certain level of pressure, and then, the compressed air was discharged out of the compressed air container, so that a compressed air engine can be operated by the discharge force of the compressed air. Thus two pairs of wings which were assembled to the compressed air engine were made perform the flapping motions, thereby generating lifting and propulsion forces. This was filed for a patent application under Korean Patent Application No. 2000-43618 (filed on Jul. 28, 2000), and based on this, a PCT application was filed under PCT Application No. PCT/KR01/00932 (field on Jun. 1, 2001).

The present inventor improved the above PCT application to develop a compressed air engine and a flying object equipped with the engine, in which only one pair of wings are provided.

OBJECT OF THE INVENTION

It is an object of the present invention to provide a compressed air engine in which a compressed air is injected into a compressed air container, and the compressed air is discharged at a certain discharge rate to generate a propulsion force, thereby making it possible to fly.

It is another object of the present invention to provide a flying object in which a compressed air is injected into a compressed air container, and the compressed air is discharged at a certain discharge rate to make a pair of wings perform flapping motions, thereby making it possible to fly.

It is still another object of the present invention to provide a flying object in which a compressed air container and a pair of wings are assembled to the compressed air engine in a simple manner, and if needed, a head part is assembled also in a simple manner, thereby making it possible to use it in a simple manner.

It is still another object of the present invention to provide a flying object in which a portable pump is used to inject the compressed air, thereby making it possible to fly in a simple manner.

It is still another object of the present invention to provide a flying object in which the pair of the wings assembled to the compressed air engine are made flap up and down to generate a propulsion force, thereby making it possible to fly.

It is still another object of the present invention to provide a flying object in which the pair of the wings assembled to the compressed air engine are made flap up and down and perform twisting motions within an angular range of about 15°.

The above objects and other objects are achieved by the present invention which is described in detail below.

SUMMARY OF THE INVENTION

In achieving the above objects, the flying object according to the present invention includes: a compressed air engine, the compressed air engine including: a top member 11 provided with an air inlet 16; an upper cylinder 12 assembled to the top member; a lower cylinder 13 assembled to the upper cylinder; a bottom member 14 assembled to the lower cylinder; an air pipe 15 connected between the top member and the bottom member, for passing of a compressed air; a shuttle 20 for performing up/down movements within a cylinder (consisting of the upper and lower cylinders) so as to make a pair of wings perform flapping motions; and a pair of pistons 21 a and 21 b for performing reciprocating movements over and under the shuttle respectively;

the pair of the wings being symmetrically and pivotally assembled to the shuttle through securing shafts so as to perform up/down movements in accordance with the up/down movements of the shuttle; and

a compressed air container 2 assembled to the bottom of the bottom member, for storing the compressed air.

In the flying object of the present invention, a compressed air is injected into the compressed air container to a certain level of pressure by using a pump, and the compressed air is discharged out of the compressed air container at a certain discharge rate, so that the upper and lower pistons 21 a and 21 b can drive the shuttle 20 up and down so as to make the pair of the wings of the shuttle 20 flap up and down, thereby generating propulsion forces.

BRIEF DESCRIPTION OF THE DRAWINGS

The above objects and other advantages of the present invention will become more apparent by describing in detail the preferred embodiment of the present invention with reference to the attached drawings in which:

FIG. 1 is a perspective view of the flying object of the present invention, in which a compressed air container is assembled to the bottom of the compressed air engine, and a pair of wings are assembled to the middle of it, the pair of the wings being at a lowered position here;

FIG. 2 is a schematic perspective view of the flying object in which the pair of the wings are at the lifted position;

FIG. 3 is a sectional view of the compressed air engine, taken along the line A-A′ of FIG. 1;

FIG. 4 is a sectional view of the compressed air engine, taken along the line B-B′ of FIG. 1;

FIG. 5A is a schematic perspective view of the top member 11, FIG. 5B is its bottom view, FIG. 5C is its sectional view, and FIG. 5D is its right side view;

FIG. 6A is a schematic perspective view of the upper cylinder 12, FIG. 6B is its frontal view, and FIG. 6C is its sectional view;

FIG. 7A is a schematic perspective view of the lower cylinder 13, FIG. 7B is its frontal view, and FIG. 7C is its sectional view;

FIG. 8A is a schematic perspective view of the bottom member 14, FIG. 8B is its plan view, and FIG. 8C is its sectional view;

FIG. 9A is a schematic perspective view of the shuttle 20, FIG. 9B is its frontal view, and FIG. 9C is its plan view;

FIG. 10A is a schematic perspective view of the piston 21, FIG. 10B is its sectional view, and FIG. 10C is its frontal view;

FIG. 11 is a schematic perspective view of one of the arms 17 for connecting the left and right wings respectively;

FIG. 12 is a schematic perspective view of a part of the wings 3 to be assembled to the arm 17; and

FIG. 13 is a schematic perspective view of the cock 306 as a means for assembling each of the wings 3 to each of the arms 17.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The flying object according to the present invention includes: a compressed air engine 1; a compressed air container 2 assembled to the bottom of the engine body, for storing the compressed air; and a pair of wings 3 a and 3 b assembled to sides of the engine body, for performing the flapping motions.

FIG. 1 is a perspective view of the flying object of the present invention, in which a compressed air container is assembled to the bottom of the compressed air engine, and a pair of wings are assembled to the middle of it, the pair of the wings being at a lowered position here. FIG. 2 is a schematic perspective view of the flying object in which the pair of the wings are at the lifted position.

The compressed air engine 1 includes: a top member 11 provided with an air inlet 16; an upper cylinder 12 assembled to the top member; a lower cylinder 13 assembled to the upper cylinder; a bottom member 14 assembled to the lower cylinder; and an air pipe 15 connected between the top member and the bottom member, for passing of a compressed air.

Within the interior of the engine body, there are accommodated a shuttle and two pistons. When these internal elements perform up/down movements, the pair of the wings perform the flapping motions. These motions are generated when the compressed air is discharged. That is, when the compressed air which has been stored within the compressed air container is discharged at a certain discharge rate, the shuttle and the pistons perform the up/down movements, and accordingly, the pair of the wings 3 a and 3 b perform the flapping motions.

The compressed air is injected through the air inlet 16 into the compressed air container 2 by using a pump or the like. That is, the compressed air which is injected by the pump (not illustrated) passes through the top member 11, the air pipe 15 and the bottom member 14 before being stored in the compressed air container 2. After being stored within the compressed air container 2, the compressed air is discharged out to drive the shuttle and the pistons.

The head part of FIGS. 1 and 2 consists of a cap having the form of a dragonfly, an airplane, a doll or the like, thereby completing a product. Here, however, they are neither illustrated nor described, but only the structure and principle of the compressed air engine will be described. The cap of the head part can take various forms, but this can be easily carried out by those ordinarily skilled in the art.

In the compressed air engine of the present invention, the shuttle 20 and the pair of the pistons 21 a and 21 b are driven within the interior of the engine body, so that the pair of the wings 3 a and 3 b can perform the flapping motions. This is illustrated in FIG. 3. FIG. 3 is a sectional view of the compressed air engine, taken along the line A-A′ of FIG. 1.

As shown in FIG. 3, the compressed air engine 10 includes: a top member 11; an upper cylinder 12; a lower cylinder 13; and a bottom member 14. A shuttle 20 is accommodated at the middle of the cylinder, and the upper and lower pistons 21 a and 21 b are accommodated over and under the shuttle 20, in such a manner that the pistons should be able to perform the up/down movements. The upper piston 21 a, shuttle 20 and lower piston 21 b may be formed in one body, if the one body reciprocates well in the upper and lower cylinders 12 and 13. A pin 22 a or 22 b and a spring 23 a or 23 b are secured to each of the pistons 21 a and 21 b, and at the outer end of each of the springs 23 a and 23 b, there is installed a bead 24 a or 24 b, for passing/blocking the compressed air. Further, there are provided hollows 25 a and 25 b for guiding the beads 24 a and 24 b respectively.

Arms 17 a and 17 b are pivotally secured to the lower cylinder by means of securing shafts 30 a and 30 b respectively. Ends of the arms 17 a and 17 b are assembled to the shuttle 20, and other ends of the arms 17 a and 17 b are assembled to the pair of the wings respectively, so that the pair of the wings can perform the flapping motions in accordance with the up/down movements of the shuttle 20.

The compressed air passes through the air inlet 16 to enter into the compressed air container 2. The compressed air thus stored in the compressed air container 2 is discharged to drive the shuttle 20 and the pistons 21 a and 21 b. This actuation principle is illustrated in FIG. 4. FIG. 4 is a sectional view of the compressed air engine, taken along the line B-B′ of FIG. 1.

Thus, the compressed air which has been injected through the air inlet 16 by the air pump (not illustrated) passes through the top member 11, the air pipe 15 and the bottom member 14 to be ultimately stored in the compressed air container 2. At the end of the air inlet 16, there is disposed a bead 161. When the compressed air is injected by the pump, the compressed air is injected while pushing the bead 161. When the pump is not activated, the bead 161 closes the air inlet owing to the internal pressure, so that the compressed air would not be discharged to the outside.

In order that the air inlet can be perfectly closed, the bead 161 should be preferably made of a soft rubber, and this can be easily carried out by those ordinarily skilled in the art.

In a state with the compressed air filled into the compressed air container 2, if the wings are hit once with hand, then the pistons 21 a and 21 b are activated. That is, if the wings 3 a and 3 b are hit downward once, then the shuttle 20 moves upward to push the piston 21 a upward. Under this condition, the bead 24 a which has been closing the air passage is pushed by the spring 23 a, so that the compressed air passes through the air pipe 15 and the top member 11 to be introduced into the hollow 25 a.

The compressed air which has been introduced into the hollow 25 a pushes the piston 21 a downward, and as a result, the shuttle 20 and the piston 21 b move downward together. When the piston 21 b moves downward, the spring 23 b pushes the bead 24 b, so that the compressed air moves along the bottom member 14 to be introduced into the hollow 25 b. The bottom member can be appropriately adjusted considering the direction of the flying object. This actuation is repeated, and thus, the shuttle 20 and the pistons 21 a and 21 b perform up/down movements until the compressed air within the compressed air container 2 is exhausted.

Now the structure and the operating principle of the compressed air engine will be described in more detail below.

FIG. 5A is a schematic perspective view of the top member 11, FIG. 5B is its bottom view, FIG. 5C is its sectional view, and FIG. 5D is its right side view.

As shown in FIG. 5A, the air inlet 16 is assembled into a hole 116 of the top member 11, while the air pipe 15 is assembled into the hole 113 of the top member 11. The upper cylinder 12 is assembled between an outer frame 111 and an inner frame 112, and there are provided holes 114, 115 and 118 so that the air can pass through. The air pipe 15 is provided with a hole 151 so as to make the air pass through, and the hole 151 has to be aligned with the hole 114 on a straight line. There is a hole 117 through which the air does not pass, but which is unavoidably formed during the preparation of the die.

FIG. 6A is a schematic perspective view of the upper cylinder 12, FIG. 6B is its frontal view, and FIG. 6C is its sectional view.

As shown in FIGS. 4 and 6, there are formed two air outlets 27 a and 28 a on the sidewall of the upper cylinder 12. Around the middle of the piston 21 a, there is inserted an O-ring 26 a. If the piston 21 a comes down to the air outlets 27 a and 28 a, then the compressed air which has been pushing down the piston 21 a is discharged through the air outlets 27 a and 28 a to the outside.

FIG. 7A is a schematic perspective view of the lower cylinder 13, FIG. 7B is its frontal view, and FIG. 7C is its sectional view.

As shown in FIGS. 4 and 7, there are formed two air outlets 27 b and 28 b on the sidewall of the lower cylinder 13. Around the middle of the piston 21 b, there is fitted an O-ring 26 b. If the piston 21 b comes up to the air outlets 27 b and 28 b, then the compressed air which has been pushing up the piston 21 b is discharged through the air outlets 27 b and 28 b to the outside.

At the opposite positions of the lower cylinder 13, there are formed holes 131 a and 131 b through which securing shafts 30 a and 30 b pass to secure a pair of arms 17 a and 17 b respectively. Meanwhile, apart by 90 angular degrees from the holes 131 a and 131 b, there is formed a hole 132 through which the air pipe 15 passes.

FIG. 8A is a schematic perspective view of the bottom member 14, FIG. 8B is its plan view, and FIG. 8C is its sectional view.

As shown in FIG. 8A, the air pipe 15 is assembled to a hole 142 of the bottom member 14. The lower cylinder 13 is assembled between an outer frame 147 and an inner frame 148, and there are formed holes 143, 144 and 145 through which the air passes. Further, the air pipe 15 is provided with a hole 152 so as to make the air pass through it, and this hole 152 has to be aligned to the hole 143 on a straight line.

There is a hole 146 through which the air does pass, but which is unavoidably formed during the preparation of the die. The compressed air container 2 is assembled to the bottom of the bottom member 14 through its holes 141 a and 141 b. This can be easily carried out by those ordinarily skilled in the art.

FIG. 9A is a schematic perspective view of the shuttle 20, FIG. 9B is its frontal view, and FIG. 9C is its plan view.

As shown in FIGS. 3 and 9, at the middle of the shuttle 20, there are secured pins 31 a and 31 b, while idlers 31 a and 32 b surround the pins 31 a and 31 b respectively.

A slot 172 of each of the arms 17 is fitted to each of the idlers, so that the arms 17 a and 17 b can be pivoted around securing shafts 30 a and 30 b respectively.

FIG. 10A is a schematic perspective view of the piston 21, FIG. 10B is its sectional view, and FIG. 10C is its frontal view.

As shown in FIG. 10, the piston 21 consists of an upper piston portion 211 and a lower piston portion 212, and between the two piston portions, there is installed an O-ring 26. On the top of the piston, there are formed a plurality of holes 214, while on the circumferential surface of the piston, there are formed a plurality of vertical channels 213.

First, when the piston 21 a comes down owing to the action of the compressed air, the compressed air exerts a pressure through the plurality of the holes 214 to make the O-ring 26 a expanded toward the outside, while the piston 21 a comes down. If the piston comes down so as for the O-ring 26 a to arrive at the positions of the air outlets 27 a and 28 a, then the compressed air is discharged through the air outlets 27 a and 28 a, with the result that the descending of the piston 21 a is stopped. At this moment, the piston 21 b starts its actuation.

This operation is repeated so that the upper and lower pistons 21 a and 21 b would perform the up/down movements alternately. As a result, the shuttle 20 performs the up/down movements repeatedly.

FIG. 11 is a schematic perspective view of one of the arms 17 for connecting the left and right wings respectively.

As shown in FIGS. 3 and 11, a securing shaft 30 is inserted into a hole 171 of the arm 17, and thus, the arm 17 is pivotally secured to a side of the lower cylinder 13. On an end of the arm 17, there is formed a slot 172 to be assembled around the idler 32. On the other end of the arm 17, there is integrally formed a connecting member 173 for connecting the wing 3 to it, and the connecting member 173 is provided with a rectangular slot 174. The connecting member may be appropriately angled to the arm considering the direction of flying of the flying object. The angle may be preferably in the range of about −50° to about +50° to the arm.

FIG. 12 is a schematic perspective view of a part of the wings 3 to be 15 assembled to the arms 17 respectively.

Wing frames 301 and 302 are integrally formed, and the connecting member 173 of the arm 17 is inserted into a hole 303 of the wing 3. If the connecting member 173 is inserted into the hole 303, the connecting member 173 is secured by using a cock 306 of FIG. 13.

The cock 306 has a fixed pin 307 and a twisting pin 308, the fixed pin 307 of the cock 306 is tightly coupled to a hole 304 of the wing 3, while the twisting pin 308 passes through a hole 305 to be coupled to the rectangular slot 174. The rectangular slot 174 has a larger cross sectional area than that of the twisting pin 308, and therefore, when the wing 3 performs the flapping motions, it also performs twisting motions within an angular range of about 40°.

Referring to FIGS. 3 and 4, the beads 24 a and 24 b serves the role of closing/opening the air passages, and therefore, they should be preferably made of a soft rubber. This can be easily carried out by those ordinarily skilled in the art.

The pair of the wings which are attached to the compressed air engine are designed such that they should be able to perform the flapping motions within an angular range of about 70°. Further, together with the flapping motions, the wings perform the twisting motions within an angular range of about 40°.

According to the present invention as described above, a compressed air engine is provided in which a compressed air is injected into a compressed air container, and the compressed air is discharged at a certain discharge rate, so that a pair of wings can perform the flapping motions. Further, there is provided a flying object utilizing the compressed air engine, in which the pair of the wings are assembled to the compressed air engine in a simple manner, a head part of a desired shape is assembled also in a simple manner, and an air pump can be used to inject the air into the compressed air engine.

In the above, the present invention was described based on the specific preferred embodiments and the attached drawings, but it should be apparent to those ordinarily skilled in the art that various changes and modifications can be added without departing from the spirit and scope of the present invention, which will be defined in the appended claims. 

What is claimed is:
 1. A compressed air engine for actuating a first and a second wing in a flapping motion, comprising: a top member having a passage formed therein for passing compressed air through a portion of the top member; an upper cylinder coupled to the top member; a lower cylinder coupled to the upper cylinder, the upper and lower cylinders defining an internal volume; a bottom member coupled to the lower cylinder; an air pipe coupled to the top and bottom members and having a passage formed therein for passing the compressed air between the top and bottom members; a shuttle positioned within the internal volume and adapted to be coupled to the first and second wings, the shuttle being adapted to move reciprocally within the internal volume in response to the compressed air thereby actuating the first and second wings; and a first and a second piston positioned within the internal volume above and below the shuttle, respectively, and adapted to move reciprocally with the shuttle in response to the compressed air.
 2. The compressed air engine recited in claim 1, further comprising a first and a second pin fixedly coupled to the respective first and second pistons, a first and a second spring disposed around the respective first and second pins, and a first and a second bead positioned at an end of the respective first and second springs, wherein the upper and lower cylinders each have a hollow formed therein for guiding the respective first and second beads between an open position in which the first and second beads facilitate passage of the compressed air to the internal volume, and a closed position in which the first and second beads inhibit passage of the compressed air to the internal volume.
 3. The compressed air engine recited in claim 1, further comprising a first and a second arm pivotally coupled to the shuttle and the lower cylinder, wherein the first and second arms are adapted to be coupled to the respective first and second wings so that the first and second wings are actuated in response to reciprocal motion of the shuttle.
 4. The compressed air engine recited in claim 1, further comprising a bead positioned proximate an end of the passage formed in the top member, wherein: the passage is adapted to received the compressed air from a pump and the compressed air urges the bead away from the passage as the passage receives the compressed air from the pump thereby permitting the compressed air to enter the compressed air engine; and the bead is urged toward the passage by the compressed air and substantially blocks the passage when the passage is not receiving the compressed air from the pump thereby preventing the compressed air from being discharged from the compressed air engine by way of the passage.
 5. The compressed air engine recited in claim 4, wherein the bead is formed from a soft rubber material.
 6. The compressed air engine recited in claim 1, wherein: a first and a second air outlet are formed on a side wall of the upper cylinder and extend between the inner volume and an exterior surface of the upper cylinder; downward movement of the first piston exposes the first and second air outlets to the internal volume and thereby permits the compressed air within the internal volume to be discharged from the compressed air engine by way of the first and second air outlets; a third and a fourth air outlet are formed on a side wall of the lower cylinder and extend between the inner volume and an exterior surface of the lower cylinder; and upward movement of the second piston exposes the third and fourth air outlets to the internal volume and thereby permits the compressed air within the internal volume to be discharged from the compressed air engine by way of the third and fourth air outlets.
 7. The compressed air engine recited in claim 3, further comprising a first and a second pin secured to a middle portion of the shuttle, and a first and a second idler positioned around the respective first and second pins.
 8. The compressed air engine recited in claim 1, wherein the first piston comprises an upper portion, a lower portion, and an O-ring positioned between the upper and lower portions, a plurality of holes are formed in the upper portion and are in fluid communication with the O-ring, and a plurality of channels are formed along an outer circumference surface of the piston and are spaced apart by a predetermined angular distance.
 9. The compressed air engine recited in claim 7, wherein: a slot is formed in a first end of each of the first and second arms and the first and second idlers are positioned within the slots formed in the respective first and second arms; each of the first and second arms has a connecting member integrally formed on a second end of thereof; the connecting members of the first and second arms are adapted to be coupled to the respective first and second wings and each have a rectangular slot formed therein; the connecting members of the first and second arms are each adapted to be inserted into a first hole formed in the respective first and second wings; the connecting members of the first and second arms are each adapted to be secured to the respective first and second wings by a cock having a fixed pin and a twisting pin that passes through a second hole in the respective first and second wings and into the slot in the respective first and second connecting members so that the first and second wings each undergo a twisting motion within a range of travel of approximately 40° when the first and second wings are actuated.
 10. A flying object, comprising: a first and a second wing; a compressed air engine comprising (i) a top member having a passage formed therein for passing compressed air through a portion of the top member, (ii) an upper cylinder coupled to the top member, (iii) a lower cylinder coupled to the upper cylinder, the upper and lower cylinders defining an internal volume, (iv) a bottom member coupled to the lower cylinder, (v) an air pipe coupled to the top and bottom members and having a passage formed therein for passing the compressed air between the top and bottom members, (vi) a shuttle positioned within the internal volume and adapted to be coupled to the first and second wings, the shuttle being adapted to move reciprocally within the internal volume in response to the compressed air thereby actuating the first and second wings, and (v) a first and a second piston positioned within the internal volume above and below the shuttle, respectively, and adapted to move reciprocally with the shuttle in response to the compressed air; and a compressed air container coupled to a bottom of the bottom member for storing the compressed air, wherein the first and second wings are symmetrically and pivotally coupled to the shuttle and to the lower cylinder by way of a respective first and second securing shaft so that the first and second wings move upward and downward with the shuttle.
 11. The flying object recited in claim 10, further comprising a cap coupled to a top of the compressed air engine.
 12. A method of imparting flight to an object having a compressed air engine coupled to a first and a second wing, comprising: injecting compressed air into a compressed-air container of the object using an air pump until the pressure within the compressed-air container reaches a predetermined level; and discharging the compressed air from the compressed air container at a predetermined rate so that a first and a second piston of the compressed air engine drive a shuttle of the compressed air engine upward and downward thereby causing the first and second wings to move upward and downward in a flapping motion that generates a force that lifts and propels the object.
 13. The compressed air engine recited in claim 1, wherein the first and second pistons and the shuttle are unitarily formed.
 14. The compressed air engine recited in claim 9, wherein a centerline of the connecting member of the first arm is positioned at an angle within the range of approximately −50° to approximately +50° in relation to a centerline of the first arm, and a centerline of the connecting member of the second arm is positioned at an angle within the range of approximately −50° to approximately +50° in relation to a centerline of the second arm.
 15. The flying object recited in claim 10, wherein the first and second pistons and the shuttle are unitarily formed. 